Background Field
Embodiments of the subject matter described herein are related generally to optical metrology targets, and more particularly to target design and manufacture for monitoring a multiple patterning process.
Relevant Background
As critical dimensions (CD) in semiconductor devices continue to shrink, the use of multiple patterning has become an important method. Multiple patterning processes, such as self-aligned doubled patterning process and self-aligned quadruple patterning process, is a technology that is used to extend photolithography beyond diffraction limit thereby enhancing feature density. As the name implies, multiple patterning processes include more than one patterning process step. For example, self-aligned doubled patterning process includes two patterning process steps: a lithography patterning step and a self-aligned spacer step. Self-aligned quadruple patterning process typically includes three patterning process steps: lithography patterning, a first self-aligned spacer step and a second self-aligned spacer step. Each of the patterning process steps in a multiple patterning process will contribute to the final critical dimension uniformity and CD distribution within the printed structure. To control the process and to achieve optimum CD distribution, it is necessary to determine the contribution of each patterning step to the final CD variation.